/*
 * @lc app=leetcode.cn id=86 lang=java
 *
 * [86] 分隔链表
 *
 * https://leetcode-cn.com/problems/partition-list/description/
 *
 * algorithms
 * Medium (53.26%)
 * Likes:    124
 * Dislikes: 0
 * Total Accepted:    17.1K
 * Total Submissions: 32K
 * Testcase Example:  '[1,4,3,2,5,2]\n3'
 *
 * 给定一个链表和一个特定值 x，对链表进行分隔，使得所有小于 x 的节点都在大于或等于 x 的节点之前。
 *
 * 你应当保留两个分区中每个节点的初始相对位置。
 *
 * 示例:
 *
 * 输入: head = 1->4->3->2->5->2, x = 3
 * 输出: 1->2->2->4->3->5
 *
 *
 */

// @lc code=start
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode partition(ListNode head, int x) {
        ListNode small = new ListNode(0), big = new ListNode(0);
        ListNode smallHead = small, bigHead = big;
        while(head != null) {
            if(head.val < x) {
                small.next = head;
                small = small.next;
            } else {
                big.next = head;
                big = big.next;
            }
            head = head.next;
        }
        big.next = null;
        small.next = bigHead.next;
        return smallHead.next;
    }
}
// @lc code=end

